Plasma cutting torch, nozzle and shield cap

ABSTRACT

A plasma torch assembly, and components thereof, is provided with optimized attributes to allow for improved torch durability add versatility. A torch nozzle is provided having a novel design, including exterior cooling channels running along a length of the nozzle. An improved inner retaining cap assembly is provided which imparts a swirl on shield gas flow. Additionally, a shield cap and outer retainer have optimized geometries to allow the torch to be made narrower to facilitate the cutting of complex 3-D shapes and bevel cuts not attainable with known mechanized plasma torches.

RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/495,996, filed on Sep. 25, 2014, entitled “Plasma CuttingTorch, Nozzle and Shield Cap,” the entire contents of which areincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

Systems and methods of the present invention relate to plasma cutting,and more specifically to arc plasma cutting using a torch assemblyhaving a novel nozzle and shielding configuration.

Description of the Related Art

The use of plasma cutting systems in various industries has grown, andas a result there is an increasing need to increase the durability andlongevity of torches and their components. This is particularly truewith regarding to some internal torch parts, such as the nozzle, andsome external torch parts, such as the shield cap. As is generallyknown, plasma cutting involves the use of high current plasma jet whichgenerates a large amount of heat during cutting and can generate spatterduring piercing or arc starting. This high heat and spatter adverselyaffects the operational life of components in the torch, which thenrequire replacement—causing downtime. Accordingly, improvements areneeded which reduce this downtime and increase the operational life oftorch components.

Further limitations and disadvantages of conventional, traditional, andproposed approaches will become apparent to one of skill in the art,through comparison of such approaches with embodiments of the presentinvention as set forth in the remainder of the present application withreference to the drawings.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention include equipment and methodsrelated to plasma cutting torches and components thereof which areimproved over known torches. Embodiments include at least improved torchnozzle geometry and configurations, improved torch geometry, torchprofile and shield cap geometry, and improved inner retaining capassembly configurations. Exemplary torches as described herein haveimproved durability, precision and operation over known torches,especially in cutting complex 3-D shapes and bevel cuts. Exemplarynozzles include exterior cooling channels and improved configuration,exemplary torches and torch shield caps have improved narrow geometriesand profiles, and exemplary inner retainer cap assemblies have improvedperformance and provide for overall improved torch geometries.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects of the invention will be more apparent bydescribing in detail exemplary embodiments of the invention withreference to the accompanying drawings, in which:

FIG. 1 is a diagrammatical representation of a known nozzleconfiguration;

FIG. 2 is a diagrammatical representation of an exemplary nozzle of thepresent invention;

FIG. 3 is a diagrammatical representation of an exemplary torch head inaccordance with an embodiment of the present invention;

FIG. 4 is a diagrammatical representation of a cross-section of anexemplary assembly of torch head components of the present invention;

FIG. 5 is a diagrammatical representation of a closer view of thecross-section of FIG. 4;

FIGS. 6A and 6B are a diagrammatical representation of an exemplaryembodiment of an inner retainer assembly of the present invention;

FIG. 7 is a diagrammatical representation of a cross-section of aportion of an exemplary embodiment of the present invention;

FIG. 8 is a diagrammatical representation of an exemplary embodiment ofan isolator ring of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the invention will now be described below byreference to the attached Figures. The described exemplary embodimentsare intended to assist the understanding of the invention, and are notintended to limit the scope of the invention in any way. Like referencenumerals refer to like elements throughout.

It is noted that for purposes of the following discussion, the systemwill be discussed as a liquid cooled, mechanized plasma arc cuttingsystem. However, exemplary embodiments are not limited to being used insuch arc cutting systems, and embodiments can be used in hand heldcutting systems as well as air cooled systems. Thus, the followingdiscussions are intended to be exemplary and informative. Further,discussions below will use terminology such as “distal” and“downstream”. In the context of this application it is understood thatthese terms mean closer to the end of the torch from which the plasma isemitted. For example, the distal end of the torch is the end of thetorch from which the plasma jet is emitted to perform cutting. Further,is something is “downstream” of another component, it is closer to thedistal end of the torch. Similarly, the use of the term “upstream” willgenerally indicate that something is further away from the distal end ofthe torch.

Because the manufacture, assembly and use of arc cutting torches isgenerally known to those of skill in the art, the details of theirassembly and components thereof will not be set forth herein.

Turning now to FIG. 1, a known cutting torch nozzle 100 configuration isshown. While nozzle configurations can vary, the nozzle 100 depicted isrepresentative of many known configurations. As generally known, thenozzle aids in focusing and directing the plasma jet from the torchelectrode to the workpiece. The nozzle 100 has a cavity and throat (notshown) which directs the plasma jet to the exit of the torch and to theworkpiece. Because the construction and use of the cavity and throat areknown, they need not be discussed herein.

As shown, the nozzle 100 has an upstream portion 111 with an upstreamend and in which a cavity opening is made so that the electrode and gasswirl ring can be inserted. The upstream portion is typically acylindrical portion having a diameter which is the maximum outsidediameter of the nozzle. In the embodiment shown, the outer surface ofthe upstream portion 110 has a first and second o-ring groove 103/105(o-rings are shown in the grooves 103/105). Downstream of the o-ringgrooves 103/1-5 is a nozzle removal groove 107 which provides a groovefor which a nozzle removal tool can be used to remove the nozzle from atorch. Downstream of the upstream portion 110 is a transition portion120. The transition portion 120 changes the outer diameter of the nozzle100 from the large upstream portion to a smaller diameter due to conicalshape of the torch end. The transition portion has an angled surface121, which is has a truncated cone shape and transitions the nozzle 100from the upstream portion diameter to a smaller diameter in for thetransition cylindrical portion 123. The transition cylindrical portion123 is used to create a shoulder portion 125 having a surface which isperpendicular to the centerline of the nozzle 100. The shoulder portion125 is used to provide a seating surface for the nozzle retainingcap—used to hold the nozzle within the torch. Downstream of thetransition portion is the distal portion 130 having a generallycylindrical shape and the smallest outer diameter of the nozzle 100. Thedistal portion 130 also has an o-ring groove 131 (o-ring shown withinthe groove) which is sealed against the nozzle retaining cap, and endsat the distal end 133 of the nozzle. The distal end 133 of the nozzle100 has the exit orifice of the nozzle throat (not shown) from which theplasma jet is emitted and directed to the workpiece. The distal end 133of the nozzle 100 also has a chamfered edge 135 which is the distal mostretaining cap seating surface. That is, the edge 135 is used to aid inseating the nozzle 100 within the retaining cap for the nozzle 100.Thus, the distal end 133 of the nozzle 100 is generally flush with thedistal end surface of the retaining cap, when the torch is assembled. Inadditional to the plasma jet, a swirl gas can be passed through thenozzle 100 and exit from the orifice in the distal end.

While the shown configuration operates acceptably, it is desirable toincrease the operational life of the nozzle. Because of their proximityto the plasma jet, the nozzle sees very high heat during torchoperation, and while the nozzle is cooled by both the swirl and shieldgas this high heat can shorten the operational life of the nozzle.Therefore, improvements are needed to increase the durability ofnozzles.

An exemplary improved nozzle of the present invention is shown in FIG.2. While the nozzle 200 has some broad similarities to the known nozzle100 configuration, there are a number of enhancements which improve theperformance of the nozzle 200. They are discussed below.

The nozzle 200 has an upstream portion 210 which has the upstream end201 of the nozzle, at least two o-ring grooves 203/205 and a nozzleremoval groove 207. The upstream portion has a general cylindrical outershape and has the largest outer diameter of the nozzle 200. Downstreamof the upstream portion 210 is the transition portion 220. Directlyadjacent to the upstream portion 210 is a curved transition portion 225which uses a curved transition from the outside diameter of the upstreamportion 210 to a cylindrical portion 223, which has a maximum outsidediameter which is smaller than the max. outside diameter of the upstreamportion 210. The curved transition portion 225 can have a arcuate shapeor can have a circular shape (i.e., having a single radius ofcurvature). This allows for a smooth flow transition between portions onthe nozzle 200. The cylindrical portion 223 has a plurality of coolingchannels 227 distributed radially around the perimeter of thecylindrical portion 223. The cooling channels 227 can begin in thecylindrical portion 223, at the transition from the curved transitionportion 225 to the cylindrical portion 223, or in the curved transitionportion 225. Additionally, in some exemplary embodiments, the coolingchannels 227 can just be located on the angled transition portion 221.For example, nozzles for low amperage applications (i.e., below 150amps) the grooves 227 can just be located on the portion 221. Thegrooves 227 are generally recesses in the outer surface of thetransition portion 220 of the nozzle 200.

The cooling channels 227 increase the overall amount of surface area ofthe transition portion 200 exposed to the coolant flow as well as aid indirecting the flow in a desired path along the nozzle 200. In exemplaryembodiments, the number of cooling channels is in the range of 5 to 12,and are distributed evenly around the circumference of the nozzle 200.In the embodiment shown in FIG. 2, the cooling channels 227 run in aline co-planar with the centerline CL of the nozzle 200 and its throat(not shown). The centerline CL passes through the center of a nozzlecavity (discussed further below). Also, it is noted that in the FIG. 2 arelative flow direction would extend from the top of the figure to thebottom, which is generally the flow of gas through the cavity. However,in other exemplary embodiments, the channels 227 can be angled to imparta swirl into the flow of cooling medium (e.g., water) passing along thelength of the nozzle 200 in the area of the cooling channels. The shapeof the channels 227 can be optimized for the desired flow pattern andcooling to be achieved. However, in some exemplary embodiments, thechannels 227 have a width which is larger than their depth. Moreover, insome exemplary embodiments all of the channels 227 have the samecross-sectional shape and flow direction, while in other embodiments afirst grouping of channels can have a first cross-sectional shape (e.g.,rectangular), while a second grouping of channels can have a differentshape (e.g., semi-circular). Moreover, some channels can be co-planarwith the centerline CL along their length, while other can be angled toimpart a swirl in the coolant flow.

In the exemplary embodiment shown in FIG. 2, the nozzle 200 has sixchannels 227 which are distributed evenly, radially around the nozzle200. As shown, the entire length of the channels 227 are co-planar withthe with the centerline CL of the nozzle. Further, the channels have agenerally rectangular cross-section, where their width is larger thantheir depth.

Downstream of the cylindrical portion 223 is an angled transitionportion 221 which is shaped like a truncated cone and reduces the outerdiameter of the nozzle 200. As shown, in exemplary embodiments of thepresent invention, the cooling channels 227 extend onto the angledtransition portion 221 and can extend to the distal end of the angledtransition portion 221, as shown. In other exemplary embodiments, thecooling channels 227 can terminate prior to the angled transitionportion 221, or along the length of the angled transition 221. Further,as shown, the channels 227 in the angled transition portion 221 remainco-planar with the centerline CL of the nozzle 200 and remain in linewith the portions of the channels 227 in the cylindrical portion 223.However, in other exemplary embodiments the portions of the channels 227in the angled transition portion 221 can be angled relative to theportions of the channels 227 on the cylindrical portion 223. Further, inthe embodiment shown in FIG. 2, the portions of the channels 227 in theangled transition portion 221 has the same cross-section as the portionsof the channels 227 in the cylindrical portion 223. However, in otherexemplary embodiments the cross-section of the channels 227 in theangled transition portion 221 is different from the portions of thechannels 227 in the cylindrical portion. For example, the portions ofthe channels 227 in the angled portion 221 can be wider and/or shallowerto aid in heat dissipating the to coolant flow out of the channels 227.In further exemplary embodiments, the cross-section of the portions ofthe channels 227 in the angled portion 221 can change along theirlength. That is, at the transition from the cylindrical portion 223 tothe angled portion 221 the cross-section of the channels 227 can beconsistent with that used in the portion 223. However, as the channels227 progress towards the distal end of the angled transition portion 221the cross-sections can vary as desired to achieve a desired performance.

As shown, downstream of the transition portion 220 is a distal portion230 of the nozzle 200. The distal portion 230 has a curved transitionportion 235 similar to the portion 225 discussed above. The curvedtransition portion 235 can have an arcuate or circular shape and reducesthe outside diameter of the nozzle 200 to a diameter of the distalportion 230 of the nozzle 200, where the maximum outside diameter of thedistal portion 230 is smaller than the smallest diameter of any of theupstream 210 and transition 220 portions. Downstream of the curvedtransition portion 235 is at least one o-ring groove 231. In otherembodiments, more than one o-ring groove can be utilized. The o-ringgroove 231 is used to secure an o-ring that seats against the retainingcap when installed. Downstream of the o-ring groove 231 is a retainingcap seat portion 236 against which a portion of the retaining cap isseated to hold the nozzle 200 in place within a torch. Downstream of theretaining cap seat portion 236 is a distal cooling portion 237, whichends at the distal end face 233 of the nozzle. The distal coolingportion 237 has a length L such that at least some of the distal coolingportion extends beyond a distal end of the nozzle retaining cap and isexposed to the shield gas flow within the torch. This allows a flow ofthe shield gas to contact the tip of the nozzle top aid in the coolingof the nozzle 200. This can be seen in at least FIG. 5, which shows across-section of an exemplary torch which includes an exemplary nozzle200. (It is noted that a discussion of the torch is set forth belowregarding FIG. 4). As shown, the distal cooling portion 237 has a lengthsuch that it extends beyond the distal end of the retaining cap 409 by adistance X. This allows at least a portion of the distal cooling portion237 to be in the shield gas flow directed in the opening 510 between theretaining cap 409 and the shield cap 303. In exemplary embodiments ofthe present invention, the distance X (measured between the distal endface of the retaining cap 409 and the distal end face 233 of the nozzle200 is in the range of 0.025 to 0.15 inches. In other embodiments,different distances can be used so long as the desired cooling can beachieved. However, the distance X should not be so long as to compromisethe flow of the shield gas through the gap 510. Further, the length L ofthe cooling portion 237 allows for the additional cooling of the end ofthe nozzle via heat transfer to the retaining cap assembly. In exemplaryembodiments, the length L (as measured from the distal end surface ofthe retaining cap seat portion 236 to the distal face 233 of the nozzle)is in the range of 5 to 15% of the overall length of the nozzle (asmeasured from surface 201 to surface 233). This allows for additionalcooling of the nozzle tip and thus extends the life of the nozzle 200.

The above discussed characteristics of the nozzle 200, both collectivelyand separately, significantly improves the cooling of the nozzle 200over known torches and improves the efficiencies of the gas flow alongthe nozzle 200. Thus, embodiments of the present invention providesignificant operational advantages over known torches. Further, theabove also allows the overall design of the torch to be optimized asfurther discussed below.

Turning now to FIG. 3, an exemplary torch 300 is shown. As explainedpreviously, the use of plasma torches in cutting operations hasincreased. This is especially true in mechanized and robotic systemswhere the torches are used to cut complex shapes. For example, torchesare used to cut complex 3-D shapes or bevel cuts. However, because ofthe complexity of known torches, and the high temperatures experiencedby torches—requiring a significant amount of cooling, known torches arerelatively bulky, especially at their distal operational end. Thisprevents known torches from being used effectively for cutting complex3-D shapes, bevels, cuts, etc. That is, it is difficult to get thesetorches into tight areas and spaces. Moreover, the wide face of thedistal ends of the torches are exposed to spatter during pierce, whichdamages the shield cap and accelerates its need for replacement.However, embodiments of the present invention address these issues byproviding a more focused and streamlined torch shape. This is depictedin FIG. 3.

FIG. 3 depicts an exemplary plasma torch 300. The torch 300 has a torchbody 305, a torch head assembly 301, a shield cap 303 and an outerretaining cap 307, where both the shield cap 303 and the outer retainingcap 307 make up the outer casing of the torch head assembly 301. Theouter retaining cap 307 secures the shield cap 303 to the torch assembly(see e.g., FIG. 4). However, unlike known torches, the geometry of thesome of the components of the torch 300 are optimized to allow for moreversatile usage of the torch 300 as well as increase the usable life oftorch components, such as the shield cap. That is, the torch 300 isnarrower and smaller than known torches.

Specifically, in exemplary embodiments of the present invention, theheight H of the torch head assembly 301 from its distal end 311 (the endface of the shield cap 303) to the upstream end 304 of the outerretaining cap 307 is less than 3.25 inches, and in some embodiments isin the range of 3.2 to 3 inches. Further, the outer retaining cap 307has a maximum outer diameter W of less than 2 inches, and in someembodiments is in the range of 2 to 1.9 inches. The maximum diameter Wis found at a central portion 307′ of the cap 307. The outer retainingcap 307 also has a stepped down outer diameter W which is less than theouter diameter W. This stepped down diameter W′ is the maximum diameterof a cylindrical downstream portion 307″ of the cap 307 where thedownstream cylindrical portion 307″ is the next adjacent cylindricalportion of the cap 307 in a downstream direction from the portion 307″having the maximum outer diameter W of the cap 307. In exemplaryembodiments of the present invention, the ratio of the stepped downouter diameter W′ to the maximum outer diameter W is in the range of0.92 to 0.95. The cap 307 is also configured such that the ratio of theheight H′ to H is in the range of 0.51 to 0.55, where the height H′ isthe maximum distance from the distal face 311 to the upper end 306 ofthe downstream cylindrical portion 307″.

The shield cap 303 is designed such that the shield cap has an exposedshield height SH which is larger than known torches. That is, inexemplary embodiments the shield cap 303 has an end face 311 diameter Dand a shield height SH such that the ratio between the diameter D andthe shield height SH is in the range of 0.25 to 0.35, where the diameterD is the diameter of the circular flat surface of the end face 311 andthe shield height SH is the exposed vertical height of the shield cap303, as measured from the end face 311 to the downstream or distal end308 of the outer retaining cap 307. In further exemplary embodiments,the ratio of D to SH is in the range of 0.28 to 0.32. Further, theshield cap has an outer angular or conical surface 312, where the angleB between the conical surface and a horizontal is in the range of 50 to65 degrees. In further exemplary embodiments, the angle B is in therange of 55 to 60 degrees. Additionally the angle A, as shown in FIG. 3,is in the range of 80 to 50 degrees. In further exemplary embodiments,the angle A is in the range of 70 to 60 degrees. The angle A is measuredbetween opposite sides of the angular surface 312 of the shield cap 303(i.e., sides that are 180 degrees from each other).

The above dimensional relationships diverge from known torchconfigurations and allow torches of the present invention to be used,more easily in complex 3-D and bevel cutting applications. Moreover, inexemplary embodiments, the dimensional relationships referenced abovecan be achieved due to, at least in part, the use of exemplary nozzlessuch as the nozzle 200 discussed above. That is, exemplary embodimentsof the nozzles, and other torch components, discussed herein allow forthe manufacture of a narrower torch. For example, the use of the coolingchannels 227 can allow the internal channels and gaps of the torch to besmaller, allowing for a tighter torch configuration. Further, exemplaryembodiments discussed herein allow for this more narrow and compacttorch design, which enhances the ability to cut complex and beveledshapes, as well as extending the life of the torch and its components.

The torch 300 and torch components herein, such as the nozzle 200, canbe used with any known cutting currents. That is, exemplary embodimentsof the present invention can be used with torches which operate with acutting current higher than 100 amps. In other embodiments, the torchesare used with a cutting current in the range of 100 to 400 amps, whilein further embodiments exemplary torches can be used with cuttingcurrents higher than 400 amps.

FIG. 4 depicts a cross-section of an exemplary torch head 301 of thepresent invention. As explained above, the torch head 301 has a shieldcap 303, which is held in position by an outer retaining cap 307.Internal to the shield cap 303 is the nozzle 200 which is held intoposition with an inner retaining cap 409. Between the inner retainingcap 409 and the shield cap 303 is a shield gas swirler 407 whichchannels and imparts a flow on the shield gas being directed between theinner retainer cap 409 and the shield cap 303. (A more detaileddiscussion of the swirler 407 and cap 409 is set forth below). Upstreamof the nozzle 200 is the electrode 411 and cooling tube 401, both ofwhich collectively are inserted into the cavity of the nozzle 200, asdiscussed previously. The plasma arc is generated from the electrode 411and the cooling tube 401 is used to direct a cooling fluid to theelectrode 411 to keep it at an acceptable operating temperature. Betweenthe electrode 411 and the nozzle 200 is a plasma gas swirl ring 405which imparts a swirl flow on the plasma gas that aids in maintaining astable arc during cutting and to cool the nozzle 200. The plasma gasswirl ring 405 has a distal end surface 405′ which seats on an innerseating surface 240 of the nozzle 200.

FIG. 5 depicts a closer view of the cross-section of the torch head 301.As can be seen, and as discussed above, the distal cooling portion 237of the nozzle 200 extends past the distal end of the inner retaining cap409 by a distance X, and has a length L which increases its heattransfer surface area. This increases the cooling of the end of thenozzle 200 and increases the life of the nozzle.

Further, as shown and discussed previously, the plasma gas swirl ring405 is inserted into the nozzle 200. Specifically, the nozzle 200 has aswirl ring cavity 250 formed by a cylindrically shaped cavity wall 251.The cavity 250 also has a horizontal seating surface 240 onto which adistal end surface 405′ of the plasma swirl ring 405 is seated. Inexemplary embodiments of the present invention the surface 240 ispositioned such that the nozzle 200 has a swirl ring cavity 250 depth CD(between the surface 240 and the upstream end 201) in the range of 0.35to 0.75 inches. In further exemplary embodiments, the depth CD is in therange of 0.62 to 0.72 inches. Further, in exemplary embodiments, thecavity depth CD is in the range of 40 to 60% of the overall length (fromsurface 201 to surface 233) of the nozzle 200. In such embodiments, theswirl ring 405 is positioned deeper into the nozzle 200 than knowntorches. This allows the swirl ring 405 and nozzle 200 of embodiments ofthe present invention to provide the desired plasma gas flow to providea stable plasma jet during cutting, especially, in torches with thegeometries and dimensional relationships discussed above.

Turning now to FIGS. 6A and 6B, an exemplary embodiment of an innerretaining cap assembly of the present invention is shown. The innerretaining cap assembly is comprised of the inner retaining cap 409 andthe shield gas swirler 407. As shown, the retaining cap 409 has aninternal cavity into which the nozzle, electrode and swirl ring areinserted (see, e.g., FIGS. 4 and 5). Additionally, as shown, the cap 409has a main portion 601 which is cylindrically shaped and has the largestexternal diameter of the cap 409. Downstream of the main portion 601 isa transition portion 610, which has a conical, or angled outer surface611, and which transitions the outer surface of the cap 409 from themain portion 601 to a cylindrical portion 603 which has a smaller outerdiameter than the main portion 601. This transition portion 610 changesthe outer diameter of the cap 409 such that the cap 409 can beaccommodated in the narrow torch configuration discussed above. Also, asshown, the transition portion 610 comprises a swirler engagement portion409′ which engages with the swirler 407. In the exemplary embodimentshown, the swirler engagement portion 409′ extends outward from thesurface 611 of the transition portion 610.

As stated above, the swirler 407 is engaged to the cap 409 via theengagement portion 409′, which aids in securing the swirler 407 betweenthe cap 409 and the shield cap 303. The swirler 407 also acts as anisolator between the cap 409 and the shield cap 303. Thus, in exemplaryembodiments the swirler 407 is made from a high heat resistantnon-metallic material. The swirler 407 is generally ring shaped suchthat the cap 409 passes through the center of the ring. Additionally,the swirler 407 has a plurality of flow channels 450 which pass from anouter diameter of the swirler 407 to an inner diameter of the swirler407. These channels 450 allow the shield gas to flow from upstream ofthe swirler 407 to the shield gas channel 510 downstream of the swirler407. This is generally depicted in FIG. 7.

As shown in FIG. 7, the swirler 407 has an inner radial profile, whichis comprised of the surfaces 407′, 407″ and the vertical surface below407″. The vertical surface below 407″ is innermost radial surface of theswirler 407 and, as shown, does not make contact with the surface 611 ofthe transition portion 610 of the cap 409. As shown, the channels 450pass from an outer radial profile of the swirler 407 to the inner radialprofile and exit through the inner surface which does not make contactwith the surface 611. Thus, the channels 450 allow for shield gas flowinto the channel 510. That is, as shield gas contacts the outer radialprofile of the swirler 407 it passes through the channels 450 and exitsinto the channel 510. FIG. 7 also depicts the swirler 407 securedbetween a protruding engagement portion 409′ of the inner retainer cap409 and the shield cap 303. The engagement portion 409′ protrudes fromthe outer surface of the inner retainer cap 409. Specifically, in theexemplary embodiment, the engagement portion 409′ has at least twoengagement surfaces 409″ and 409″′, which engage with two correspondingengagement surfaces 407′ and 407″, respectively, on the swirler 407.This engagement provides both horizontal and vertical support for theswirler 407. Additionally, in exemplary embodiments, an outer surface407″′ and distal end surface 407″″ of the swirler 407 engage,respectively, with surfaces 303′ and 303″ on the inner surface of theshield cap 303. The shield cap retaining surfaces 303′ and 303″ form arecessed engagement portion in an inner surface 710 of the shield cap303 to aid in securing the swirler 407, and again restrains the swirler407 in both a horizontal and vertical direction. As the shield gas flowsfrom its upstream source it is directed to the channels 450 and thechannels direct the flow into the shield gas channel 510. In theembodiment shown in FIG. 7, the channels 450 are oriented horizontally,such that their respective centerlines are perpendicular relative to thecenterline CL of the torch. However, in other exemplary embodiments, thechannels 450 can be angled such that their respective entrances (from ashield gas flow perspective) is positioned further from the distal endof the torch and end of the cap 409, then the respective shield gasexits of the channels 450. That is, in using FIG. 7 as a reference thechannel 450 would slope downward from right to left, where the entranceto the channel 450 (in the outer profile of the swirler 407) would behigher than the exit of the orifice (in the inner profile of the swirler450). Thus, in such embodiments, the channels 450 such that their exitsare closer to the distal end of the cap 409. In exemplary embodiments,the channels 450 have a circular cross-section and have a diameter whichallows for the desired amount of air flow. In other exemplaryembodiments, the cross-section of the channels 450 can be non-circular.In exemplary embodiments, as shown in FIG. 7, the entrance to thechannels 450 is positioned on the same surface of the engagement surface303′. In some embodiments, the diameters or cross-sections of thechannels 450 can all be the same, whereas in other embodiments thediameters or cross-sections of the channels 450 can be different. Forexample, there can be embodiments where some channels have a firstdiameter, and other channels 450 have a second smaller or biggerdiameter.

FIG. 8 depicts a cross-sectional view of two alternative embodiments ofthe swirler 407. As shown, the channels 450 are distributed radially andevenly around the circumference of the swirler 407. The number ofchannels should be sufficient to provide the desired flow of shield gasto the channel 510 and for the cutting operation. In exemplaryembodiments, the number of channels ranges between 10 and 20. Further,the channels 450 are oriented in the swirler 407 so as to impart a swirlflow to the shield gas such that the shield gas is swirling in thechannel 510. This aids in providing a shield gas which aids instabilizing the plasma arc during a cutting operation. As shown, inexemplary embodiments the channels 450 are oriented such that theirrespective centerlines CCL are offset by a distance XD from a line PCLparallel to the centerline CCL that passes through the centerpoint ofthe swirler CL. As shown in FIG. 8, the swirler 407 on the left has anoffset XD which is less than that of the swirler 407 on the right. Thelarger the offset XD the larger the amount of swirl imparted to theshield gas flow. In the embodiments shown each of the channels have thesame offset XD. However, in other exemplary embodiments some of thechannels have a first offset XD, while others of the channels 450 have asecond offset XD, which is different. That is, in exemplary embodiments,the offset XD of the respective channels 450 is optimized to provide thedesired swirl flow for the shield gas. In exemplary embodiments of thepresent invention the offset distance XD is in the range of 0.03 to 0.86inches. In further exemplary embodiments, the offset distance XD is inthe range of 0.054 to 0.57 inches.

By incorporating features and attributes described above, exemplarytorches described herein are able to have an significantly optimizedprofile and geometry (e.g., as described relative to FIG. 3) and,therefore, provide an optimized cutting torch that has improved life andcutting attributes. This improvement over known technologies isachievable due to novel improvements discussed herein, as without suchnovel features the enhancements herein could not be obtained. Thus,exemplary embodiments described herein represent a significantimprovement over known torch configurations, and provide improvedperformance, durability and versatility as compared to known torches.

While the invention has been particularly shown and described withreference to exemplary embodiments thereof, the invention is not limitedto these embodiments. It will be understood by those of ordinary skillin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the invention as definedby the following claims.

What is claimed is:
 1. A plasma cutting torch assembly, comprising: anouter retaining cap having a central portion which has a first maximumouter diameter which is the largest outer diameter of the outerretaining cap, and a downstream cylindrical portion which is coupled tothe central portion and has a second maximum outer diameter which issmaller than the first maximum diameter, where the downstreamcylindrical portion is positioned closer to a distal end of the plasmacutting torch assembly than the central portion; and a shield cap whichis secured to the plasma cutting torch assembly by the outer retainingcap, and having a distal end face with a flat circular surface having adiameter D, and an angular outer surface which extends from the distalend face to a distal end of the outer retaining cap, and where theshield cap has an exposed outer surface height SH such that a ratio ofthe diameter D to the height SH is in a range of 0.25 to 0.35, where theheight SH is measured vertically from the distal end face to the distalend of the outer retaining cap, wherein the angular outer surface has aconical shape and where the angular outer surface has an angle in arange of 50 to 65 degrees relative to a horizontal line passing throughthe distal end face of the shield cap.
 2. The plasma cutting torchassembly of claim 1, wherein a ratio of the second maximum outerdiameter to the first maximum outer diameter is in a range of 0.92 to0.95.
 3. The plasma cutting torch assembly of claim 1, wherein the angleis in a range of 55 to 60 degrees.
 4. The plasma cutting torch assemblyof claim 1, wherein the ratio of the diameter D to the exposed height SHis in a range of 0.28 to 0.32.
 5. The plasma cutting torch assembly ofclaim 1, wherein the first maximum outer diameter is less than 2 inches.6. The plasma cutting torch assembly of claim 1, further comprising atorch body.
 7. The plasma cutting torch assembly of claim 1, whereineach of the outer retaining cap and the shield cap are configured suchthat the torch assembly has a first height H, as measured verticallyfrom the distal end face of the shield cap to an upstream end of theouter retaining cap, and a second height H′, as measured vertically fromthe distal end face of the shield cap to a distal end of the downstreamcylindrical portion having the second maximum outer diameter, wherein aratio between the second height H′ to the first height H is in a rangeof 0.51 to 0.55.
 8. The plasma cutting torch assembly of claim 7,wherein the first height H is in a range of 3 to 3.2 inches.
 9. Theplasma cutting torch assembly of claim 1, further comprising a torchhead assembly.
 10. The plasma cutting torch assembly of claim 9, whereinthe shield cap and the outer retaining cap make up an outer casing ofthe torch head assembly.
 11. A plasma cutting torch assembly,comprising: a shield cap, where the shield cap includes: a distal endface with a flat circular surface having a diameter D; and an angularouter surface extending from the distal end face, wherein the shield caphas an exposed outer surface height SH such that of ratio of thediameter D to the height SH is in the range of 0.25 to 0.35, and whereinthe angular outer surface has a conical shape, where the angular outersurface has an angle in the range of 50 to 65 degrees relative to ahorizontal line passing through the distal end face of the shield cap.12. The plasma cutting torch assembly of claim 11, wherein the angle isin a range of 55 to 60 degrees.
 13. The plasma cutting torch assembly ofclaim 11, wherein the ratio of the diameter D to the exposed height SHis in a range of 0.28 to 0.32.
 14. The plasma cutting torch assembly ofclaim 11, further comprising an outer retaining cap, wherein the shieldcap is configured to be secured to the plasma cutting torch assembly viathe outer retaining cap, and wherein the outer retaining cap includes acentral portion having a first maximum outer diameter which is a largestouter diameter of the outer retaining cap, and a downstream cylindricalportion coupled to the central portion and having a second maximum outerdiameter which is smaller than the first maximum outer diameter, andwhere the downstream cylindrical portion is positioned closer to adistal end of the plasma cutting torch assembly than the centralportion.
 15. The plasma cutting torch assembly of claim 14, wherein aratio of the second maximum outer diameter to the first maximum outerdiameter is in a range of 0.92 to 0.95.
 16. The plasma cutting torchassembly of claim 14, wherein the first maximum outer diameter is lessthan 2 inches.
 17. The plasma cutting torch assembly of claim 14,wherein each of the outer retaining cap and the shield cap areconfigured such that the torch assembly has a first height H, asmeasured vertically from the distal end face of the shield cap to anupstream end of the outer retaining cap, and a second height H′, asmeasured vertically from the distal end face of the shield cap to adistal end of the downstream cylindrical portion having the secondmaximum outer diameter, wherein a ratio between the second height H′ tothe first height H is in a range of 0.51 to 0.55.
 18. The plasma cuttingtorch assembly of claim 17, wherein the first height H is in a range of3 to 3.2 inches.
 19. The plasma cutting torch assembly of claim 14,further comprising a torch head assembly.
 20. The plasma cutting torchassembly of claim 19, wherein the shield cap and the outer retaining capmake up an outer casing of the torch head assembly.